Research On The Organic Photovoltaic Cells Based On Single Walled Carbon Nanotubes And Graphene

Carbon nanotubes (CNTs) are one dimensional nanomaterials of a high conductivity; they have been widely used to fabricate opto-electronic devices such as field effect trainsistors, organic photovoltaic cells, etc. The overall performance of the photovoltaic device based on the acceptor of SWNT is very low because of the highly aggregation of SWNT. We prepared a photovoltaic device based on an active layer of novel naphthyl substituted PPE/SWNTs, in which good dispersion of SWNTs in PPE matrix is obtained. With a device structure of ITO(～17 ? sq-1)/ PEDOT: PSS(30 nm)/ PPE: SWNTs(100 nm)/ LiF(1 nm)/ Al(80 nm), we obtained a Voc of 1.04 V, Jsc of 0.25 mA-2,ηof 0.05%, which is relatively good than a control device based on P3PT/SWNTs (Voc=0.6 V, Jsc=0.30 mA-2,η=0.05%).Graphene is a single atom layered 2 dimensional single crystal shows zero band gap and high electron mobility of 15,000 cm2 V-1 s-1 at room temperature. We fabricated a photovoltaic device based on soluble graphene and P3HT/P3OT. The soluble graphene can be well dispersed in the polymer matrix and shows strong electronic interaction and energy transfer. Through an annealing treatment, the energy conversion efficiency has been greatly increased. Under a simulated illumination of AM1.5G at 100 mW intensity, we obtained a Voc of 0.70 V, Jsc of 4.0 mA-2, of 1.1% on an device of ITO (~17 ? sq-1)/PEDOT: PSS(40 nm)/P3HT: graphene(100 nm)/LiF(1 nm)/Al(70 nm).Charge collection is one of the important factors influencing the performance of the photovoltaic device. In order to improve the hole collection, a buffer layer of PEDOT:PSS is often used to modify the ITO electrode. Therefore the electronic properties of PEDOT:PSS layer have great influence in the device performance. We use graphene to modify the PEDOT:PSS active layer and fabricated a photovoltaic device having a structure of ITO/buffer layer (40 nm)/ P3HT:PCBM (1:0.6, 100 nm)/LiF (1 nm)/Al (70 nm). Such device shows 3.8% power conversion efficiency, ~ 80% higher than that of the control device based on the pristine PEDOT:PSS buffer layer.